Question

+ Name of Organism Gram Reaction Glucose Sucrose Lactose Mannitol Nitrate Citrate BEA H2S indole Motility MR VP Catalase ADC LDC ODC PDA Urease Gelatin Oxidase Aerobic requirements Alcaligenes forces Negative -- -- + d . Citrobacter bracki Obligate aerobe Negative A/G -- A/G A/G + - . +- Facultative Citrobacter freunde Negative A/G d d AG + - d Citrobacter koser (orig. diversus Nerative Facultative A/G d d AIG + + + d d Edwardsiella tarda Facultative Negative ANG -- -- -- + + . + + - Enterobacter aerogenes Facultative Negative A/G A/G A/G AG + + - 1. + + + V Enterobacter cloacae Facultative Negative A/G A/G A/G A/G + d + d V Facultative Escherichia col Negative AIG d A/G ANG + + + + - + + - - Klebsiella pneumoniae Facultative Negative AIG ANG A/G ANG + + + Morganella morgan Facultative Negative A/G . + + + + + Proteus mirabilis Facultative Negative A/G + . - + d + + + Proteus vulgaris - Facultative Negative A/G A/G - + + +- + + + + Providencia start Facultative Negative A d / + . d Facultative Salmonello enterica Negative AIG . A/G + . - d + + - - - Sevroti marcescens Facultative Negative Ald A/? A? . V Shigellement Facultative Negative A. A/ + - Facultative Shigelle sonne Negative A/ - A/? + Facultative +

Identify the unknown bacteria using the following information:

* Glucose fermenter. Only acid/ no gas

* Mannitol fermenter. Acid + gas

* Non-lactose fermenter

What bacteria could this be?

Answer 1

This bacteria is Shigella sonnei.

Glucose is fermented producing acid but no gas by bacteria such as Providencia stuartii, some strains of Serratia marcescens, Shigella flexneri and Shigella sonnei.

Out of these bacteria, species which may produce acid and gas from mannitol are Serratia marcescens and Shigella sonnei.

Both of them are non-lactose fermenter.

However, the best option is Shigella sonnei because all strains will be positive for the above tests.